Security camera systems, also referred to herein simply as security systems, are well known in the art and are widely used, in both residential and business settings, to monitor and safeguard a designated environment from intruders. One well-known type of security system includes at least one video surveillance camera that is connected to a common digital recording device, such as a digital video recorder (DVR) or network video recorder (NVR), by a cable or other conventional communication path. In use, each camera continuously compiles video of the monitored area and processes the video for transmission to the common video recording device. The common recording device, in turn, receives the encoded video signal compiled from each camera and decodes the signal into a corresponding digital video stream.
The two principal types of video surveillance cameras that are traditionally utilized in security systems are analog cameras and digital cameras, which are also commonly known in the art as Internet Protocol (IP) cameras. Analog and digital cameras differ primarily in that analog cameras process the compiled video signal to be transmitted to the common recording device in analog form, whereas digital cameras process the compiled video signal to be transmitted to the common recording device in digital form. As a consequence, it has been found that the two aforementioned types of video cameras differ principally in cost, with analog cameras being generally less expensive than digital cameras.
Commonly, security camera systems of the type as described above are designed to detect any relevant movement within the monitored environment, such as the presence of an individual. Upon detecting such movement within the area under surveillance, the system is designed to initiate a predefined response, such as the commencement of video recording and/or activation of an alert signal. In this manner, security camera systems serve as effective tools in safeguarding a monitored area from unauthorized intruders.
Motion detection technology is often used to detect the presence of an individual within the monitored environment. The detection of motion within the designated area is commonly achieved by examining pixel changes in the compiled digital video streams. Specifically, a central controller in the common recording device is programmed to measure pixel changes in each digital video stream. Any detected pixel change that exceeds a predefined threshold is considered a motion detection event and, as such, causes the recording device to undertake the previously determined motion detection response.
Although well-known and widely used in the art, security systems that rely solely on pixel changes to detect relevant movement within the monitored environment have been found to suffer a notable shortcoming with respect to accuracy. Specifically, it has been found that monitoring pixel changes in video streams frequently results in relatively inconsequential movement triggering a motion detection event. Examples of irrelevant action which may induce a motion detection event include, inter alia, (i) variances in light within the monitored environment (e.g., resulting from lights being turned on/off, sunlight changes and the like), (ii) movement of animals, insects, dust or other small elements within the monitored environment, and (iii) movement of elements in the background (e.g., rain, wind-induced movement of trees, shrubs or swings) or immediately outside of the monitored environment (e.g., a moving car or rain seen through a window within the designated area). As can be appreciated, this detection of inconsequential movement within the monitored environment often results in unnecessary recordings and alerts, which is highly undesirable.
In view thereof, it has become increasingly common for security systems to monitor infrared radiation variances within the designated environment, rather than monitor pixel changes in a digital video feed, in order to detect relevant movement within the area under surveillance (e.g., the presence of a person). For instance, it is known in the art for security systems to equip a digital Internet Protocol (IP) camera with a pyroelectric infrared radial (PIR) sensor circuit.
In use, the PIR sensor circuit measures infrared light that radiates from objects in its field of view (e.g., thermal energy produced from a person) in relation to the remainder of the monitored environment. The digital output signal from the PIR sensor circuit is then combined with the streaming video signal during signal processing prior to transmission to the common recording device. The recording device then analyzes the infrared radiation signal component of the mixed signal. If any thermal energy variance is detected that can be attributed to, inter alia, the standard body temperature range, the recording device initiates the predefined motion detection response. In this manner, an effective method for detecting a notable motion event within the monitored environment can be achieved.
As can be appreciated, the use of PIR sensors in security camera systems to detect relevant movement within a monitored environment has been found to suffer from a couple notable shortcomings.
As a first shortcoming, PIR sensors are traditionally used with digital camera systems due to the processing capabilities of the signal processor responsible for combining and conditioning the digital PIR output signal with the digital video stream. However, as referenced briefly above, digital cameras have been found to be relatively expensive in nature, largely due to the cost associated with the advanced signal processor as well as the signal communication channels commonly used in conjunction therewith (e.g. Ethernet cables).
As a second shortcoming, security camera systems which rely solely upon the detection of infrared radiation within a defined thermal energy range to initiate a trigger event have been found to be experience reliability issues. Specifically, it has been found that unforeseen variances in infrared radiation within the monitored environment can often be attributed to conditions other than relevant movement (e.g., the presence of people) and, as such, can induce false trigger events. Examples of non-human action which may induce a variance in infrared radiation within the designated temperature range include, inter alia, (i) rapid changes in sunlight radiation within the field of view, (ii) intense thermal energy changes caused by equipment within the monitored environment (e.g., a burner), and (iii) sun, lightning or other bright light reflecting off highly reflective surfaces (e.g., glass or a pool) toward the PIR sensor.